The present invention is particularly concerned with the provision, especially in a can making machine, of improved joint soldering mechanism but it will be recognized that application of the invention is not limited to side seams nor even necessarily to cans of any particular configuration.
Side seam soldering of cans has been disclosed, for example, in U.S. Pat. Nos. 3,255,945; 3,370,772; 3,371,837; 3,371,838; 3,371,839 and 3,384,286. In general, the can making details and arrangements described therein have received good commercial acceptance. They involve feeding of cylindrical can bodies with their side seams in a predetermined path, and the application of molten solder to the joint of each seam as it progresses.
In U.S. Pat. No. 3,190,528 there is disclosed an applicator nozzle having a discharge orifice for applying solder to a seam groove, and a V-guide for riding in the groove to restrict can movement during the soldering. One approach to the problem of dealing with impurities such as solder oxides and slag in the molden solder to be fed from a reservoir and through a nozzle is described in the above-mentioned U.S. Pat. No. 3,371,837. Another approach seeking to prevent flux-caused clogging of a soldering nozzle orifice is taught in the referenced U.S. Pat. No. 3,371,838. The teaching of the latter, by a gaseous (air or otherwise) enveloping of the applicator orifice and the solder streaming therefrom, attempts to avoid orifice restriction and blockage. Thus, though the general desirability of preventing solder oxidation and joint contamination has been known for some time, no entirely satisfactory solution to the problem has as yet been developed, so far as known.
Looking further back in the prior art, it is also noted that an old system (sometimes still used) which included conveyorized movement of can bodies to be side seam soldered also included, usually between means for preheating the interlocking seam edges and means for after-heating their soldered joint, a solder bath wherein an applicator roll having an undulating circumferential surface transferred molten solder to the seam joint as the roll surface moved transversely of the joint, i.e. across the direction of travel of the side seams. In such earlier systems it was customary to provide, downstream of the after-heat section, a cloth-covered buffing roll for wiping off excess solder. Since the applicator undulations were intended to, and did, work across the seam at several points thus attempting to force surplus solder into the opening between the seam plies, the wiping roll operating in air subsequently usually oxidized the solder setting up in the joint as well as removed bits of the excess and oxidized solder.